The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
As an oil well is being drilled, a sonde is usually lowered periodically into the borehole to measure characteristics of the earth formations it traverses. Typically, a logging cable supports and moves the sonde within the borehole, carries power for the sonde, and relays control instructions and data between the sonde and instrumentation and control facilities at the surface of the earth. As measurements and measuring instruments have become more sophisticated, there is a demand for cables with high power capabilities and higher data transmission rates.
To provide a cable with strong mechanical strength, a hepta cable consisting of six conductors around a central conductor is provided. While a hepta cable provides improved mechanical stability, the hepta cable has limited telemetry capabilities and power transmission capabilities.
A cable of a quad configuration is known to have high-power capabilities. As shown in FIG. 14, a wireline cable 200 of a quad configuration includes four large high power conductors 202 (only one indicated). Four smaller helical conductors 204 (only one indicated) are disposed in the cavities formed in adjoined large high power conductors 202. The interstices formed between the large high power conductors 202 and the smaller conductors 204 may be filled with a filler material to bind the conductors together. After the filler material 206 fills in the interstices, a tape 208 is then wrapped around the conductors 202, 204 and the filler material 206 to form a cable core. A protective jacket 210 including two layers of armor wires 212 and 214 are then wrapped around the cable core for providing a desirable mechanical strength, thereby forming a cable assembly 200.
The cable of a quad configuration, however, has disadvantages in mechanical instability. During the well logging process, the smaller optical conductors tend be pushed further into the cavities between the adjoined larger power conductors and are susceptible to damage and short circuit.
Accordingly, there is a need for an opto-electrical cable having improved mechanical strength, mechanical stabilities, power transmission and telemetry capabilities. Further, as more complex and versatile downhole tools having distinct requirements are used in oil exploration, there is also a need for an opto-electrical cable which can be easily manufactured to have desired telemetry and power transmission capabilities to suit a specific application.